CBS 107, 13-15 (2011). HPTLC of 5-hydroxymethylfurfural (HMF) in honey on silica gel, prewashed with methanol - water 6:1, with ethyl acetate. Quantitative determination by densitometry in absorbance mode at 290 nm. Optional detection by immersion in p-aminobenzoic acid reagent followed by heating at 110 °C for 5-10 min. The hRf value of HMF was 80. The calibration function was polynomial in the range of 0.8-80 ng/band whilst Michaelis Menten 2 regression was suitable for higher concentrations. The LOD of HMF in honey samples was 0.75 mg/kg (12 µL applied) and the LOQ 2.4 mg/kg. The method complies with the requirement of max. 15 mg/kg of HMF in honey. The results with this method were compared with those obtained by the spectrophotometric Winkler method and by HPLC-UV and mean differences were minor (3.3 % or 0.9 mg/kg). Complementary confirmation by HPTLC-MS online coupling. HMF zones identified under UV were eluted and analyzed by ESI-MS in full-scan and SIM mode.

J. of Chromatogr. A 1218 (20), 3089-3084 (2011). Comparison of the separation of the structurally related angiotensin-converting enzyme (ACE) inhibitors lisinopril, cilazapril, ramipril and quinapril and their corresponding active diacid forms (prilates) by conventional TLC on silica gel with the separation on monolithic ultra-TLC (UTLC) phase. Technical modifications of the commercially available equipment for sample application, development and detection were necessary for the use with UTLC plates. Development in a modified horizontal developing chamber with ethyl acetate - acetone - acetic acid - water 16:4:1:2. Detection by absorbance measurement at 220 nm and after exposure to iodine vapors under daylight, as well as by image analysis. As a result the monolithic layer was more efficient for the separation of structurally similar polar compounds, such as prilates, than conventional silica layers. Confirmation of the identity of the compounds by ESI-MS after their online extraction from the UTLC and TLC plates.

Planta Med. 75, 1000 (2009). TLC and HPTLC of Mezereon (Daphne mezereum) bark extracts and scopoletin, umbelliferone, mezerein, and daphnetoxin on silica gel with various mobile phases containing toluene, ethyl acetate, and formic acid at different proportions. Detection under UV 254 and 366 nm and visible light. The applied procedure may be proposed for an updated and optimized TLC identification test of the homeopathic monograph of Daphne mezereum L.

Ham. Ex D. Don, Myricaceae. J. Planar Chromatogr. 23, 326-331 (2010). HPTLC of myrecitin and stem bark extracts on silica gel with toluene - ethyl acetate - formic acid - methanol 15:15:3:2. Quantitative determination by absorbance measurement at 268 nm. Linearity was between 0.4-2.0 µg/band. The limits of detection and quantitation were 93 ng and 284 ng/zone. The intra-day and inter-day precision of the method was in the range of 0.14-0.55 %. The recovery of myrecitin at three concentrations was in the range of 98.9-100.1 % and the average recovery was 99.3 %.

J. Liq. Chromatogr. Relat. Technol. 32, 2893-2905 (2009). HPTLC of albiflorin, paeoniflorin, (beta)-catechin, benzoyloxypaeoniflorin, benzoylpaeoniflorin, beta-sitosterol in the roots of Radix paeoniae Rubra (1) and Radix Paeoniae Alba (2) on silica gel with chloroform - ethyl acetate - methanol - formic acid 30:5:10:1 for high polarity components and toluene - ethyl acetate - methanol - formic acid 20:4:2:1 for lipophilic components. Detection by spraying with vanillin - sulphuric acid - ethanol 1:5:95, followed by heating at 105 ºC for 10 min. Qualitative determination by densitometry at 366 nm. The HPTLC fingerprints allowed differentiation between the roots of (1) and (2).

J. Planar Chromatogr. 24, 482-486 (2011). HPTLC of (-)-epicatechin and procyanidin B2 in chocolates on cellulose with n-propanol - water - acetic acid 20:80:1. Detection by immersion for 1 s in 4-dimethylaminocinnamaldehyde. Quantitative determination by densitometry at 655 nm. The samples contained 13 mg/100 g each of (-)-epicatechin and procyanidin B2 with a relative standard deviation of 5.8 and 4.2 % (n = 6), respectively. The calibration curves were polynomial in the range of 2-30 ng/zone for (-)-epicatechin and 4-60 ng/zone for procyanidin B2. LOD was 0.2 ng/zone (0.7 pmol) and 2 ng/zone (3.5 pmol) as well as LOQ was 0.4 ng/zone (1.4 pmol) and 4 ng/zone (7 pmol) for (-)-epicatechin and procyanidin, respectively.

J. AOAC Int. 93, 1757-1767 (2010). HPTLC of four mixtures of 21 pesticides on RP-18 by PPEC under different operating conditions. The samples were separated on a prewetted RP-18 phase with acetonitrile - buffer. Detection under UV light at 254 or 366 nm and in the range of 197 to 1033 nm with a DAD densitometer. Reproducible retention of pesticides was obtained; the reported separations are over 10 times faster than the corresponding separations by TLC.

J. Planar Chromatogr. 24, 507-512 (2011). HPTLC of flavonoids (quercetin and kaempferol) and biflavonoids (sciadopitysin, ginkgetin, and bilobetin) in aqueous methanolic extracts of Ginkgo biloba on RP-18 by double development with 1) acetonitrile - water - methanol - formic acid 20:20:1:0.005 and 2) acetonitrile - water - methanol - formic acid 20:17:1:0.005. Quantitative determination by densitometry in absorption mode at 254 nm. LOD and LOQ were in the range of 0.12-0.37 and 0.60-1.85 µg/zone, respectively. Linearity was found over the concentration range of 0.5-4.0 µg/zone for quercetin, kaempferol, sciadopitysin, ginkgetin, and bilobetin with correlation coefficients r = 0.9990, 0.9922, 0.9939, 0.9974, and 0.9706, respectively. Average recoveries were in the range of 97.7-100.4 %.